[Qgis-user] Using/visualizing 3D data (Z values)

[Marco Hugentobler]

Hi Paul

Unfortunately, the current geometry system does not handle z- and
m-values in a sound way.
Some tools consider z and others don't. M-values are even more difficult
as they cannot be accessed by the QGIS API (z-coordinates can be read by
parsing the binary format of the geometry).

An overhaul of the geometry system is planned for version 2.

Regards,
Marco

On 05.12.2011 10:42, Paul Lens wrote:
>  Hi all,
>
>  1. I made a TIN surface, using the interpolation plugin, from a point
>  shapefile (with "ALTITUDE" field) and  3D line shapefiles. I lost time
>  trying to extract the relevant lines from the line shapefiles without
>  loosing the 3D information (Z values of the nodes).
>  If I remember well, I first used "Merge Layers" from the mmqgis
>  plugin, and it kept the Z information. Than, I used the Intersection
>  command in the Vector menu, and the Z information was lost. Finally,
>  after manually selecting the relevant lines and using "save as", I got
>  the expected 3D line shapefile keeping the Z values.
>  Is this loss of Z information a known limitation of the gdal vector
>  commands in QGIS (vector menu) and is this limitation affecting all
>  these commands? Or did I do something wrong?
>
>  2. In a second step, I wanted to be able to easily see (through
>  labeling a Z field) or ask (with the identify command) those Z values
>  from the 3D lines, so as to fine tune the interpretation of the
>  topography.
>  Again the gdal tool (in Vector menu) "Node Extraction" lost all Z
>  information.
>  Is there a workaround to create a point shapefile with a Z field? Or,
>  at least, to keep the Z values in a point shapefile, rasterize it so
>  as to be able to visualize the Z value using  the "Identify" command
>  on the raster?
>
>  Thanking all the developers for this wonderful program,
>


-- 
Dr. Marco Hugentobler
Sourcepole -  Linux&   Open Source Solutions
Churerstrasse 22, CH-8808 Pfäffikon SZ, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee


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